In an article published in the May 2000 issue of ACTA Biochimica of Biophysica Sinica (Ma et al), scientists from the Institute of Molecular Biology in China discuss the potential of using ceramic chips.
The Ma et al article notes that ceramic has a chemistry similar to silicon. This enables the same surface chemistry used for DNA arraying on glass chips to be used for ceramic chips. Ceramic has a unique surface structure that allows more DNA to be arrayed. Because more DNA can be arrayed, ceramic chips can be used several times through probe stripping without significant sensitivity loss. In addition, ceramics are commonly used in semi-conductor and computer chip manufacturing. This enables unique electronic devices to be embedded in the chip to monitor and control DNA hybridization.
The work of the Chinese scientists prompted scientists in North America to experiment with ceramic chips. There is wide range of advanced ceramic materials. It can be divided into non-oxide and oxide ceramics. The family of non-oxide includes; alumina, alumina nitride, silicon carbide, silicon nitride. The oxide family includes alumina, zirconia and sapphire. Alumina is the most widely used advanced ceramic materials with good corrosion resistance at reasonable price. 99.6% aluminum oxide substrate, which is commonly referred to as “thin film ceramic substrate, has a surface finish of 8 to 12 microinches after lapping and polishing. 96% aluminum oxide substrate, which is commonly referred to as “thick film ceramic substrate”, has similar thickness and flatness characteristics but a surface finish of 15 to 20 microinches after lapping and polishing.
It was discovered that surface irregularities on the ceramic chips were incompatible with fluorescence laser scanning devices used to scan the surface of the substrate. For example, the laser scanner sold under the Trade Mark “ChipReader” manufactured by Virtek Vision of Hamilton, Ontario, Canada. Although macromolecules adhere to the surface of the ceramic chips, fluorescent compound becomes trapped in grooves and defects. This requires harsher washing conditions than normal, resulting in detachment of desired molecules from the surface of the substrate. This does not provide the sensitivity necessary to accurately read arrays of DNA and macromolecules, such as proteins and antibodies.